Which of the following events occurs first during a voluntary muscle contraction?
A)The T-tubules depolarize,causing calcium to be released from the sarcoplasmic reticulum.
B)Calcium is resequestered (taken up)into the sarcoplasmic reticulum.
C)Tropomyosin moves,exposing the actin active sites.
D)The innervating alpha-motor neuron reaches an action potential.

Question

Quizplus · Accepted Answer

The innervating alpha-motor neuron reaches an action potential first during a voluntary muscle contraction, which triggers a series of events leading to muscle contraction. The action potential travels down the axon of the alpha-motor neuron and triggers the release of acetylcholine at the neuromuscular junction, which stimulates depolarization of the muscle fiber. This eventually leads to the release of calcium from the sarcoplasmic reticulum and the movement of tropomyosin, exposing the actin active sites and allowing for myosin to bind and initiate muscle contraction. The resequestration of calcium back into the sarcoplasmic reticulum occurs after muscle contraction has ended.

Which of the Following Events Occurs First During a Voluntary